Photosensitive silver halide layers and process

ABSTRACT

This disclosure concerns a process of producing photographic images by photoexposing a photosensitive silver halide layer of less than two microns thickness and subsequently physically developing the exposed layer to obtain a visible image. The preferred silver halide layers are of a thickness of less than one micron. The resulting photo-images are characterized by extremely high resolution, especially resolution required for holographic imaging and reproduction. Additionally, the images are adherently bonded to the film substrate.

United States Patent 91 Gracia et al.

[ Nov. 27, 1973 PHOTOSENSITIVE SILVER HALIDE LAYERS AND PROCESS inventors: Robert F. Gracia, Scituate; Richard A. Laughrey, Woburn', Paul F. Tuohey, Quincy, all of Mass.

Assignee: Itek Corporation, Lexington, Mass.

Filed: June 12, 1970 Appl. No.: 45,927

Related US. Application Data Continuation-in-part of Ser. No. 744,631, July 15, 1968, abandoned, Continuation-impart of Ser. No. 862,912, Oct. 1, 1969.

Foreign Application Priority Data July 14, 1969 Great Britain 35,290/69 References Cited UNITED STATES PATENTS /l970 Woodward et a1. 96/33 [1971 Sieg et al. 96/33 [1972 Berman et al. 96/35 2,184,599 12/1939 Jenny et a1 96/86 3,252,798 5/1966 Jonker et a1... 96/48 PD 2,627,088 2/1953 Alles et a1 6/84 2,698,241 12/1954 Saner..... 96/87 2,698,242 12/1954 Saner 96/87 3,425,830 2/1969 Sanders 96/1.5

3,152,903 10/1964 Shepard et al 96/64 2,766,119 10/1956 Freedman et al 96/86 2,115,339 4/1938 Mason 96/86 3,471,288 10/1969 Herman 96/27 Primary Examiner-Norman G. Torchin Assistant Examiner-Edward C. Kimlin Attorney-Homer 0. Blair, Robert L. Nathans and W. Gary Goodson [5 7] ABSTRACT his d ure qqnsr ns a p oc s t P ducin P119 graphic images by photoexposing a photosensitive silver halide layer of less than two microns thickness and subsequently physically developing the exposed layer to obtain a visible image. The preferred silver halide layers are of a thickness of less than one micron. The resulting photo-images are characterized by extremely high resolution, especially resolution required for holographic imaging and reproduction. Additionally, the images are adherently bonded to the film substrate.

A 24 Claims, No Drawings PHOTOSENSITIVE SILVER HAL-[DE LAYERS AND PROCESS This application is a continuation-in-part application of Ser. No. 744,631, filed July 15, 1968, now abandoned and Ser. No. 862,912, filed Oct. 1, 1969.

There is a need for silver halide layers which give high order resolution, for example as required in holography. Additionally, particularly in the production of photographic film, printing plates, nameplates and electrical printed circuits and components, there is need for silver halidelayers which yield metal images that are adherently bonded to the layer substrates.

The present invention provides a solution to the said needs and additionally provides this solution by way of extremely rapid and facile processing chemistry.

DESCRIPTION OF THE INVENTION This invention relates to the production of photo, graphic metal images by physical development of very thin light-sensitive silver halide layers of thicknesses of less than about 2 microns and preferably less than about 1 micron. The silver halide is preferably dispersed in a binder. Additionally, the invention provides a new process for producing the very thin, lightsensitive layers for use in producing photographic metal images by physical development, aswell as the products produced thereby.

The very thin, light-sensitive silver halide layers are produced by coating a low solids emulsion preferably containing less than 10 percent and more preferably less than 5 percent total solids on a suitable substrate to obtain very thin silver halide layers, the amount of the silver halide preferably being from about 100 and more preferably from about to about grams/per liter of the emulsion. It is necessary only to have sufficient silver halide present to obtain a latent image upon exposure which is amplifiable by physical development, preferably to produce goodimage adhesion to the support. The coating emulsion is made'up using conventional binders, such as gelatin, polyvinyl alcohol and the like, with the selected silver halide, the ratio of silver halide to binder being from as high as 20/ l to as low as l/20 but preferably, for best results, from about 3/1 to about l/3. Slow, fast, or intermediate photographic response silver halide layers can be formed by control of the particle size as is generally known and well documented in the literature. The silver halide emulsion can be stoichiometrically balanced or contain excess of either silver ions or halide ions depending on the end use or the shelf-life requirements, as is also well known. For example, for slow photographic response, large excesses of halide in the emulsion are avoided since these favor larger silver halide particle size through ripening and, as is well known, the larger particles lead to fast photographic response.

The production of photographic metal images is accomplished by contacting the very thin, light-sensitive layer after photoexposure with a physical developer. As is generally well-known, a physical developer is composed of a reducible metal ion and a reducing agent therefor. In physicaldevelopment, the reducible metal ion, after reduction, forms the greater part of the developed photographic image, rather than the silver halide of the photosensitive emulsion, although the resulting image does contain at least light-reduced silver particles and may contain additional silver depending on the reducing system employed. In other words, the silver halide of the photosensitive layer hardly contributes to the final visible image. Such physical development is distinguished from the usual chemical development associated with silver halide photoprocessing which is predicated on the formation of visible images solely utilizing the silver of the silver halide in the photosensitive layer. Classically, the silver halide in the photosensitive layer is solubilized using complexing agents such as soluble thiosulfates or thiocyanates and the image is formed by reduction of the solubilized silver halide using conventional reducing agents, i.e., developers.

The use of very thin, light-sensitive silver halide layers provides substantial advantage in many areas of photographic production of visible images. The said layers permit ready and facile physical development to produce very desirable properties in the metal images obtained. For example, the metal images are readily produced in a form very desirable for printed circuit and planographic master production, i.e., the image obtained can be more readily produced as a lustrous continuous and conductive metal image than can be obtained with thicker photosensitive layers. Further, with the aforesaid very thin photosensitive layers, after physical development, the image produced is more adherently bonded to the substrate when compared to images produced with layers of 2 microns or higher thickness. This is of particular advantage when the substrate is metal plate. In producing printing plates, a strongly adherent continuous lustrous metal image is more readily obtained than with thicker photosensitive layers. The thin, light-senitive silver halide layers of this invention also give rise, on development, to exceptionally thin metal images which are especially suitable where distortion due to layer thickness or metal image thickness is to be avoided as in photogrammetry, as in production and reproduction of holographic images where high resolution is an absolute requirement. The present new thin layers give images which are of exceptionally high resolution.

The use of such thin photosensitive layers as in the present invention also leads to considerable advantage in thepackaging of film where, conveniently, the film is usually packed in rolls, with the present film requiring less space than prior art films designed for the same use. Thus, in the same package space, more of the present film can be made available than with conventional film.

Additionally, the fixing and drying time is significantly improved. This is especially important, for example, in the high speed processing of photographic film (e.g., at speeds of feet/min. or greater). An additional advantage is that the manufacture of the film is simplified since the photosensitive layer drys and sets more readily and has less rheology problems than with film having thicker layers. The film can be more economically manufactured since conventional coating equipment can be used such as film subbing equipment rather than the relatively slow and more costly photographic coating equipment.

One of themore important advantages of the photosensitive medium of this invention is that it has the capability of being very high photographic speed such as for taking pictures in a camera and also capable producing extremely high resolution and at the same time having the capability of high or low gamma images. This unusual combination of properties makes possible improved high resolution original aerial photographs,

forming a printing plate by exposing directly onto a photosensitive plate from a computer-driven CRT or other exposure device. Photographic film having improved archival quality is also possible due to the excel-' lent adhesion possible between the image and the support. Thus, abrasion which might remove the binder does not necessarily remove the image from the film.

PREFERRED EMBODIMENTS OF THE INVENTION The silver halide employed is that which is conventionally used in photography and is made in the conventional way, i.e., by reaction in aqueous systems of soluble silver salt such as silver nitrate or sulfate and a soluble alkali metal halide, such as sodium chloride, sodium bromide or sodium iodide, or corresponding potassium salts. The formation of the particles of silver halide can be controlled to permit any desired particle size, ranging from as little as 30 to 50 Angstrom units up to conventional particle size. Preferred methods are those which encourage fine particle size, usually less the 0.5 microns. For general convenience, such fine particle size is obtained by using systems of low solids content, preferably at approximately 5 percent total solids (including the weight of silver halide and the binding agent) and rapidly mixing the soluble alkali metal halide solution with the soluble silver salt solution, usually at about room temperature, for convenience.

The binder employed can be any of those conventionally used in forming siler halide emulsions. Preferably, the binder should be wettable by aqueous solutions to a sufficient degree to permit rapid processing of the exposed layer. Preferred binders are the usual gelatin, so common in silver halide films, polyvinyl alcohol, polyacrylates, including polyacrylic acids, casein and the like. The use of polyvinyl alcohol is especially preferred where fine particle size of the silver halide is desired since the binder apparently discourages ripening, i.e., growth of the silver halide particles which occurs on standing.

The binder, of course, is added to the aqueous system used to form the silver halide particles, as a matter of convenience. In addition, other materials can be added to the binder-aqueous system as desired to obtain specific effects in the photosensitive layer during or after exposure. For example, sensitizing dyes, thiourea, toners, mercuric salts or the like can be added for their known photographic effects, e.g., thiourea to assist in formation of black photographic images, and the sensitizing dyes to alter the spectral response of the layer on photoexposure.

After preparation, the emulsion is then coated on a substrate. The coating process can be any of those commonly employed, e.g., air knife, roller coating or similar such coating means. With proper settings, a coating weight of about 0.5 grams per square meter can be readily attained and gives a uniform layer of about 0.5 microns. By adjustment, thinner layers, e.g., 0.2 0.3 microns and even lower, can be made. Thicker layers up to one micron and higher present no problem to those skilled in the art. The optimum layers are produced with a ratio of silver halide to hinder of from about 3/1 to about 1/3.

The preferred thin layers, i.e., of thickness below one micron, usually contain as silver halide, approximately 0.3 grams of silver per square meter.

The physical developers which are preferred are socalled stabilized physical developers, particularly those which are most effective at acid pH value, i.e., below pH 7. Especially preferred are the so-called mono-bath physical developers which are stabilized. Monobath physical developers consist of a single solution of reducible metal ion and the reducing agent therefor. On prolonged use, there is apparently a tendency to formation of undesired side products. Stabilized monobath physical developers are known in tthe art and usually include surfactants or similar such materials which prolong the life of the physical developer. One of the basic problems with physical developers is the tendency toward decomposition with formation of insoluble materials that contaminate photographic emulsions or otherwise are undesirable in terms of their adverse affect on the acceptability and/or aesthetics of the photographic image. The surfactants apparently minimize such decomposition, i.e., stabilize the physical developer.

The optimum results attainable with the physical developers is at pH values below 7, i.e., in acid media, usually at about pH 1-5. Higher pH values should be avoided because of the possible adverse effect on the surfactants which are sensitive to high pH values.

In the physical developers employed, the reducible metal ion is usually of a metal at least as noble as copper, e.g. silver, copper, gold, platinum, palladium and the like. However, other metal ions such as nickel and tin can also be used, with appropriate reducing agents. Reducing agents for copper, silver and like noble metal ions are readily determinable and are fully described in the literature.

A particularly effective monobath physical developer is composed of silver ion and, as reducing agent therefor, the ferrous-ferric ions developer which is wellknown to the art.

For best results, the monobath physical developers are usually prepared immediately before use to increase the useful life of the system. The surfactants are added during formation of the monobath to obtain maximum stabilization.

The physical developers may contain additional materials which assist in formation of the desired type of photographic image. Thus, for example, complexing agents for the metal ion to be reduced may be present, or toners which effect the physical appearence of the resulting photographic image.

In lieu of the described monobath physical developers, there may be used separate solutions of the reducible metal ionand the selected reducing agent. For example, the physical developer can be made up of separate solutions of silver ions, and Metol. The exposed layer is first immersed in the silver ion solution and subsequently in the Metol solution. The results obtained are quite acceptable but the separate steps are undesirable for obvious reasons of time and labor waste. Additionally, the results are not always as reliable with reference to the reproducibility, desirable photographic image characteristics as those attainable with monobath physical developers, especially in stabilized form.

One or both of the oxidizing and reducing agent components of the developer may be present in the photosensitive medium prior to exposure, if desired.

The physical developer, irrespective of monobath, separate solutions or stabilization, can be applied to the photosensitive layers in the form of viscous solutions or gels with essentially the same results as the liquid systems. The efiiciency of viscous solutions, and particularly gels, make these forms of the physical developer particularly desirablein commercial use of the present new thin photosensitive layers.

Altemately, the image forming materials (physical developer) may be incorporated in the photosensitive layer of this invention. Thus, a decomposable metal salt such as silver EDTA may be incorporated in the photosensitive layer as described in copending U. S. Application Ser. No. 45,909 filed June 12, 1970 in the name of John Manhardt, entitled Print-out Processes and Imaging Media Therefor, now abandoned. Also, an oxidizing agent and a reducing agent such as described in U. S. Reissue Pat.. 26,719 may be utilized as the image forming materials in the photosensitive medium. The advantages of a high resolution print-out photographic system requiring no wet processing are apparent.

The sensitometry of the present films can be altered to meet a desired photographic use. For example, the photoresponse and gamma can be changed in the emulsion if different mixtures of silver halides are used, and- /or by increasing the silver halide particle by allowing ripening to take place. Gamma can be controlled by ad-v dition of known materials, e.g., cadmium salts, or by regulating the amounts of surfactants and/or pH of the physical developer.

In a particularly preferred form of the invention, the exposed thin layer is first chemically developed, e.g., by contact with known chemical developers such as hydroquinone, metol, and the like, after which physical development, as hereinbefore described, is used to obtain the final image. Such chemical development usually leads to a faint silver image which is then amplified by physical development. The intermediate chemical development, followed by physical development, results in an increase in the effective speed. The higher effective speed is accompanied by a slight decrease in gamma. The intermediate chemical development is particularly desirable to obtain continuous tone images in the physically developed film. In addition, when the metal ions of the physical developer are otherthan sil-v ver ions, the intermediate chemical development step gives substantially better results in the physical development step. I

The intermediate chemical development of the exposed thin silver halide layer leads to a more adherent metal image obtained by physical development. This adherence of the metal image is, of course, in reference to the substrate, and, in photographic media comprising a metal substrate, this improved adherence to the metal substrate is;especially deirable, particularly in making printing plates, nameplates, electrical circuits,

and the like.

In another preferred form of the invention, the thin, photosensitive layer is applied to a hydrophobic substrate such as cellulose acetate or a polyester film base, e.g., polyethylene terephthalate, without the use of the subbing layer or with a spring subbing layer rather than the two or more which is so common to such substrates. Furthermore, the coatings'can be applied with conventional coating equipment such as equipment for applying subbing layers rather than expensive and slow photographic coating equipment. The applied silver halide layer is comprised of a binder principally consisting of material normally designated subbing binder, or subbing material which preferably comprises a mixture of development to take place in. Emulsion polymers or combinationsof these polymers with gelatin are preferred. Examples of such subbing materials are vinylidene chloride copolymers, acrylate polymers and copolymers polyvinyl acetal polymers, and polybutadiene copolymers. Suitable such copolymers include the vinylidene chloride copolymers containing at least- 35 percent by weight of vinylidene chloride, e.g., the poly(vinylidene chloride and acrylic or methacrylic ester or nitrile and itaconic acid) compounds described in Alles and Saner US. Pat. No. 2,627,088, the polyisocyanates and polyisothiocyanates described in Saner US. Pat. No. 2,698,242, the mixtures of (a) polyester of ethylene glycol, terephthalic acid and polyethylene glycol or saturated aliphatic dicarboxylic acid, soluble in CHCl-CCl and ,(b) organic -polyisocyanate or polyisothiocyanate described in Saner US. Pat. No. 2,698,241 and the polyesters of aforesaid item (a) described in Alles and Saner US. Pat. No. 2,698,239. The various copolymers of vinylide ne chloride mentioned are described in US. Pat. No. 2,627,088, including methods of preparation, and the said patent is incorporated hereby by reference for the said disclosure. Additional subbing materials are the butadiene copolymers as described in Belgium Pat. No. 721,469.

An especially preferred embodiment is a sheet material wherein the binder additionally comprises gelatin.

The following examples further illustrate the invention.- Unless otherwise indicated, all parts are parts by weight.

Example 1 Solution A Solution B Distilled H,O 84.0 Distilled H,O 84.0 10% at NaCl 30.9. 10% aq. AgNQ, 81.5 5% PVOH 14.0 5% PVOH 14.0

(Solution B is not prepared until immediately before the described use, i.e., freshly prepared before mixing with Solution A.) Solution A is added to Solution B under good agitation within about 5 seconds total addition time, at room temperature. The mixture is then sonified (Bronson Sonifier) for 4 minutes at about watts. Then, 248 parts of 5 percent PVOl-l solution is added to the mixture under good agitation and agitation is continued for about 5 minutes thereafter. Subsequently, the mixture is filtered through a five micron bag to obtain an emulsion of the following characteristics: Emulsion Constants:

1:2 rates of silver chloride to PVOH 10 percent excess chloride 4.5 percent total solids 12.4 g. silver chloride/liter pH 5.9 to 6.2

viscosity 6 to 8 cps The emulsion can then be coated on a substrate by either air knife, roller coating or similar coating means. Good results are obtained using a roller coater with hard rubber rolls. With proper settings, a coating weight of 0.5 g./m can readily be obtained.

A polyester film having a single vinylidene chloride copolymer subbing layer is so coated and thoroughly dried by heating at about 27C for ten minutes. The coated film is then exposed and developed in the following stabilized physical developer:

grams Solution 1 Ferrous Ammonium Sulfate 78.4 bring to l Ferric Nitrate 32.3 liter with Citric Acid 80.0 distilled water Solution ll Distilled Water 100.0

Synthrapol N 1.0 Annac 120 1.0

Developer Solution l 125.0

Solution [I 25.0 3N Silver Nitrate 6.0

A lustrous, coherent, metallic image is obtained on the film.

Example 2 The following solutions are prepared as in Example 1:

SOLUTIONS A B C Distilled Distilled 30% Phenyl Water-92.0 Water-92.0 Mercuric 10% NaCl30.9 10% AgNO;,-8l.5 Acetate-1.15 5% Lemol l698--206.0 5% Lemol 'l6-98 206.0

The solutions are mixed in the following order: Solution A is added to Solution B, Solution C is added to the mixture, and the mixture is stirred and filtered as in Example l, to obtain and emulsion of the following characteristics: Emulsion Constants: l

1.3 Silver Chloride to Binder percent Excess Chloride 4.5 percent Total Solids 9.7 Grams Silver Chloride per Liter 1 percent Mercury on Binder Solids pH 7.7 to 8.0

Viscosity 6 to 8 cps.

The combined solutions are used to coat a subbed, polycoated paper stock with a roller coated and the paper then is exposed and developed as in Example 1. The silver chloride particle size (average) ranges from 50 to 200 A and the layer thickness is about 0.1 micron.

Example 3 An emulsion containing 8 percent excess silver at a total solids content of 4.4 percent is prepared from the following solutions:

Solution l Solution ll 18 cc. 3N AgNO;, 3 gm. NaCl 210 cc. H,O 210 cc. H,O

72 gm. Lemol 16-98 (10%) 72 gm. Lemol 16-98 Solution ll is added to Solution 1 rapidly with stirring and the mixture is then sonified for 5 minutes. The

emulsion is then used to coat any desired substratefilm, paper, aluminum metal at a coating weight of about 0.5 g/m i.e., at a thickness of one micron or less.

The coated substrate is then exposed and process as in Example 1.

Example 4 The following solutions are prepared:

Solution A Distilled H 0 85 ml. Sodium Chloride 6.67 gm. Solution B Distilled H 0 250 ml. Silver Nitrate 15 gm. K&K lnert Gelatin 20 gm. Formaldehyde 1 gm. (3%) Example 5 The procedure of Example 2 is repeated with the added step of chemical development prior to the physical development. The chemical development is by immersion in a standard silver halide developer, e.g., Kodak D-l9 or D-76, to obtain a faint silver image.

After physical development, the resulting image is more detailed than that of Example 2, i.e., lower gamma.

Example 6 The procedure of Example 5 is repeated substituting a metal substrate for the paper substrate and utilizing the following physical developer:

Parts CuSO, (10% aq.) NmEDTA (10% aq.) NaCl The resulting image is adherently bonded to the substrate.

Example 7 The procedure of Example 1 is repeated with the added step of chemical development as in Example 5, i.e., prior to physical development, and the resulting is of greater detail than that obtained in Example 1. The photographic gamma is about 1.5 whereas that of the Example 1 image is greater than 3.

Example 8 The procedure of Example 1 is repeated with the ex exception that the physical developer is the following solution:

CuSO Ascorbic Acid Example '9 The procedure of Example 1 is repeated with the exception that the physical developer is the following solution:

AgNO

Metol Citric Acid Comparable results are obtained.

Example The procedure of Example 1 is repeated to form a.

printed electrical circuit consisting of silver.

The printed circuit is then amplified to an additional thickness of 1-5 mils. by electrolytic deposition of copper using a conventional 'copperizing bath, e.g., CuSO /H SO solution at coating electrical current.

The metal printed circuit is adherently bonded to the substrate. 1

Example 1 1 The procedure of Example 2 is repeated using a brush-grained anodized aluminum sheet as substrate in lieu of paper.

The resulting plate is then wiped with a dispersion of mercaptobenzothiazole (e.g.,) phosphoric acid (5 ml.

' 85 percent) and dodecylammonium chloride (0.5 g.) in

one liter of water. The silver image will now accept lacquer or ink depending on whether it is to be used as a color image'(by' inclusion of color in the lacquer) or as a printing plate.

The metal image is adherently bonded to the aluminum substrate.

7 Example 12 .and the liquid is heated to 60C. In another flask are placed successively '800 ccs ofisopropanol, 144 g of N- vinyl-pyrrolidone, N-terL-butylacrylamide and 2,520 g of vinylidene chloride. The mixture is sitrred and brought to dissolution by gentle heating.

Through the droppingfunnel a solution is added of 21.6 of ammonium persulphate in 400 ccs of water. Immediately pumping of the monomer solution into the rection flask is started. The rate of pumping is such that after 75 min. all the monomer solution is pumped over. Together with the monomer solution a further amount of ammonium persulphate solution is added dropwise (64.8 g in 1,200 ccs of water). During the whole reaction period the temperature of the mixture is maintained at 60C while refluxing. After all the monomer has been added, again an amount of 21.6 g of ammonium persulphate dissolved in 400 ccs of water is added at once. After refluxing, stirring is continued for another 30 min. at 60C, whereupon the reaction mixture is cooled to room temperature.

In order to precipitate the copolymer of vinylidene chloride, N-tret.-butylacrylamide,' N-butyl acrylate,

and N- vinylpyrrolidone (70:23:314), the latex formed is 108 g of n-butyl acrylate, 830 g of poured into a mixture of 40 liters of 10 percent aqueoussodium chloride solution and 40 liters of methanol while stirring. The fine grainy precipitate which is obtained is repeatedly washed with water and finally dried. I

An amount of 2.5 g of the vinylidene chloride copolymer formed above are dissolved in a mixture of ccs of butanone and 10 ccs of nitroethane. The solution obtained is warmed to 25C and coated on a plate of polymethyl methacrylate in such a way that 0.75 to 1.0 of copolymer is present per sq.m., This layer is dried at room temperature.

A copolymer latex is prepared as follows:

In a 20 liters autoclave are placed successively:

water boiled under nitrogen 10.2 i 10% aqueous solution of oleylmethyltauride 0.6 l 10% aqueous solution of the sodium salt of heptadecyl-disulphobenzimidazole 0.6 l azodiisobutyronitn'le 6 g methyl methaci'ylate 1500 g butadiene 1500 g After sealing of the autoclave, the strongly stirred emulsion is polymerized for 6 hr. at 60C. This polymerization is slightly exothermic for a short while. Then the pressure drops rapidly. The polymerization is finished under reduced pressure. The latex of the copolymer of butadiene and methyl methacrylate (50:50) is then freed from residual traces of monomer by blowing at 60C and under a slight vacuum an air current above the latex. Then the latex is cooled and filtered.

The above latex copolymer is now used to prepare an emulsion of the following composition:

SOLUTION A SOLUTION B Distilled H 0 84.0 Distilled l-l,o 84.0

10% aq. NaCl 30.9 10% aq. AgNO; 81.5

5% gelatin 14.0 5% gelatin 14.0

Solution Ais added to Solution B with good agitation over a time period of approximately 5 to 10 seconds. Then, 248 parts of a 5 percent latex copolymer prepared above is added to the mixture under good agitation. Theagitation is continued for 30 minutes. The emulsion is then filtered and isready for coating. The coating may be applied by an air knife, roller coating or other means. The coat weight should be kept at approximately 0.5 grarns per square meter or below.

The subbed polyester film having a single vinyl copolymer subbing layer is so coated and thoroughly dried. The coat of the film is then exposed and devel oped as described in Example 1.

Example 13 An emulsion is prepared as described above in Example 12 except that the latex emulsion polymer used is either AC-22 or AC-33 as obtained from Rohm & Haas. The emulsion is coated to an identical coat weight and manner as in Example 12 and is exposed and processed as described in Example 1.

What is claimed is:

-1. In a photosensitive medium suitable for use as a printing plate, the improvement wherein the photosensitive layer comprises silver halide and a binder, said layer being of less than about 2 microns thickness deposited directly on a metal substrate, said layer having been deposited on said substrate by coating said substrate with an emulsion comprising silver halide and binder. I

2. Medium as in claim 1 wherein the layer thickness is less than about one micron and wherein the emulsion is an aqueous emulsion.

3. Medium as in claim 1 wherein the layer thickness is less than about 0.5 micron and wherein the layer was applied to the substrate by roller coating the aqueous silver halide emulsion.

4. Medium as in claim 1 wherein the amount of silver as silver halide is about 0.03 g/m and wherein the weight ratio of silver halide to binder is from about 1/3 to about 3/1.

5. Medium as in claim 1 lwherein the substrate is a grained, anodized aluminum substrate.

6. Medium as in claim 3 wherein the substrate is a brush grained, anodized aluminum substrate suitable for use for preparing a printing plate by exposure and contact with a stabilized, silver ion, ferrous/ferric physical developer.

7. Medium as in claim 6 wherein the silver halide has a particle size of less than about 0.5 micron.

8. Medium as in claim 1 wherein the silver halide is silver chloride having an excess chloride content.

9. Medium as in claim 2 wherein the amount of silver halide present on the substrate based on weight of silver is less than about 0.5 glm 10. Medium as in claim 3 wherein the particle size of the silver halide is from about 50 to about 200 A.

11. in a photosensitive silver halide medium, the improvement wherein the photosensitive layer comprises silver halide and a binder, said layer being less than 1 micron in thickness deposited directly on a metal substrate, said layer having been deposited on said substrate by coating said substrate with an emulsion comprising silver halide and a binder.

12. Medium as in claim 11 wherein the thickness of the photosensitive layer is less than about 0.5 micron.

13. Medium as in claim 11 wherein the silver halide particle size is less than about 500 A.

14. Process of forming a metal image adherently bonded to a metal substrate comprising (1) mixing silver halide and a binder to form a photosensitive emulsion, (2) coating this emulsion directly on a metal substrate in an amount such that the dry thickness oil the resulting photosensitive layer w'iii'ii'i'ss than about 2 microns, (3) drying said emulsion, (4) imagewise exposing the coated substrate, and (5) contacting the support with a physical developer comprising a solution of metal ions and a reducing agent for these metal ions to selectively deposit the metal in exposed portions of the photosensitive layer.

15. Process as in claim 14 wherein the substrate is a grained, metal substrate.

16. Process as in claim 15 wherein the metal is aluminum.

17. Process as in claim 16 wherein the substrate is a brush grained, anodized substrate.

18. Process as in claim 15 wherein the step of contacting with the physical developer is prolonged fora time period sufficient to form a metal image suitable for use as a printing plate.

19. Process as in claim 18 wherein the thickness of the photosensitive layer is less than about 0.5 micron.

20. Process for making a printing plate comprising (1) preparing an aqueous photosensitive emulsion comprising mixing silver halide and a binder, 2) coating said emulsion directly on a grained metal support, (3) drying the coating to form a photosensitive layer having a thickness of less than about 1 micron, (4) exposing the coated support to an image pattern of activating radiation, and (5) contacting the medium with a stabilized physical developer comprising a solution of metal ions, a reducing agent for said metal ions and an ionic surfactant such that metal is deposited in exposed portions of the coated substrate.

21. Process as in claim 20 wherein the thickness of the emulsion is less than about 0.5 micron and wherein the metal support is anodized aluminum.

22. Process as in claim 21 wherein the silver halide has a particle size of less than about 500 A.

23. Process as in claim 22 wherein the silver halide is silver chloride having an excess of chloride ions present and wherein the binder comprises polyvinyl alcohol or gelatin.

24. Process as in claim 20 wherein the silver halide I is present in an amount of about 0.03 g/m based upon the weight of silver present.

UNITED STATES PATENT OFFICE v CERTIFICATE OF COREQTEN Patent No. 3 775 l 1 4 I Dated November 27 ,I l 973 v Inventor(s) Robert F. Gracia et al I I It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 3l, delete siler and insert in its place-- silver--. 7

Column 4, line l0, delete "tthe" and insert in its place-- the--.

Column 4, line 47, delete "effect" and insert in its place-- affect.

Column 5, line 20, after "present" please insert--thin--.

Column 5, line 53, delete 'd eirable" and insert in its placedesirabl e v Column 5, line 60, delete "spring" and insert in its place-- singl e--.

Column 6, line- 41 delete "5" and insert in its place--5%--.

Column 9, line 53, delete"rection" .and insert in its place-- reaction--.

Column l0, line l0,aifter "l .0 please insert- 9.".

, Column ll line l4, delete '"ll" and insert in its place--l--.

Signed and sealed this 11th day of March 1975 V M (SEAL) Attest:

v C. MARSHALL DANN RUTH C. MASON (j Attesting Officer: ifi rfid agi FORM PO-lOSO (10-69) USCOMM'DC 60376-1 69 U45. GOVERNMENT PRINTING OFFICE: 1569 O--356334 

2. Medium as in claim 1 wherein the layer thickness is less than about one micron and wherein the emulsion is an aqueous emulsion.
 3. Medium as in claim 1 wherein the layer thickness is less than about 0.5 micron and wherein the layer was applied to the substrate by roller coating the aqueous silver halide emulsion.
 4. Medium as in claim 1 wherein the amount of silver as silver halide is about 0.03 g/m2 and wherein the weight ratio of silver halide to binder is from about 1/3 to about 3/1.
 5. Medium as in claim 1 1wherein the substrate is a grained, anodized aluminum substrate.
 6. Medium as in claim 3 wherein the substrate is a brush grained, anodized aluminum substrate suitable for use for preparing a printing plate by exposure and contact with a stabilized, silver ion, ferrous/ferric physical developer.
 7. Medium as in claim 6 wherein the silver halide has a particle size of less than about 0.5 micron.
 8. Medium as in claim 1 wherein the silver halide is silver chloride having an excess chloride content.
 9. Medium as in claim 2 wherein the amount of silver halide present on the substrate based on weight of silver is less than about 0.5 g/m2.
 10. Medium as in claim 3 wherein the particle size of the silver halide is from about 50 to about 200 A.
 11. In a photosensitive silver halide medium, the improvement wherein the photosensitive layer comprises silver halide and a binder, said layer being less than 1 micron in thickness deposited directly on a metal substrate, said layer having been deposited on said substrate by coating said substrate with an emulsion comprising silver halide and a binder.
 12. Medium as in claim 11 wherein the thickness of the photosensitive layer is less than about 0.5 micron.
 13. Medium as in claim 11 wherein the silver halide particle size is less than about 500 A.
 14. Process of forming a metal image adherently bonded to a metal substrate comprising (1) mixing silver halide and a binder to form a photosensitive emulsion, (2) coating this emulsion directly on a metal substrate in an amount such that the dry thickness of the resulting photosensitive layer will be less than about 2 microns, (3) drying said emulsion, (4) imagewise exposing the coated substrate, and (5) contacting the support with a physical developer comprising a solution of metal ions and a reducing agent for these metal ions to selectively deposit the metal in exposed portions of the photosensitive layer.
 15. Process as in claim 14 wherein the substrate is a grained, metal substrate.
 16. Process as in claim 15 wherein the metal is aluminum.
 17. Process as in claim 16 wherein the substrate is a brush grained, anodized substrate.
 18. Process as in claim 15 wherein the step of contacting with the physical developer is prolonged for a time period sufficient to form a metal image suitable for use as a printing plate.
 19. Process as in claim 18 wherein the thickness of the photosensitive layer is less than about 0.5 micron.
 20. Process for making a printing plate comprising (1) preparing an aqueous photosensitive emulsion comprising mixing silver halide and a binder, (2) coating said emulsion directly on a grained metal support, (3) drying the coating to form a photosensitive layer having a thickness of less than about 1 micron, (4) exposing the coated support to an image pattern of activating radiation, and (5) contacting the medium with a stabilized physical developer comprising a solution of metal ions, a reducing agent for said metal ions and an ionic surfactant such that metal is deposited in exposed portions of the coated substrate.
 21. Process as in claim 20 wherein the thickness of the emulsion is less than about 0.5 micron and wherein the metal support is anodized aluminum.
 22. Process as in claim 21 wherein the silver halide has a particle size of less than about 500 A.
 23. Process as in claim 22 wherein the silver halide is silver chloride having an excess of chloride ions present and wherein the binder comprises polyvinyl alcohol or gelatin.
 24. Process as in claim 20 wherein the silver halide is present in an amount of about 0.03 g/m2 based upon the weight of silver present. 